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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/9] xen: arm: parse modules from DT during early boot.
On Fri, 2012-12-07 at 17:30 +0000, Stefano Stabellini wrote:
> On Thu, 6 Dec 2012, Ian Campbell wrote:
> > The bootloader should populate /chosen/modules/module@<N>/ for each
> > module it wishes to pass to the hypervisor. The content of these nodes
> > is described in docs/misc/arm/device-tree/booting.txt
> >
> > The hypervisor parses for 2 types of module, linux zImages and linux
> > initrds. Currently we don't do anything with them.
> >
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > ---
> > v4: Use /chosen/modules/module@N
> > Identify module type by compatible property not number.
> > v3: Use a reg = < > property for the module address/length.
> > v2: Reserve the zeroeth module for Xen itself (not used yet)
> > Use a more idiomatic DT layout
> > Document said layout
> > ---
> > docs/misc/arm/device-tree/booting.txt | 25 ++++++++++
> > xen/common/device_tree.c | 86
> > +++++++++++++++++++++++++++++++++
> > xen/include/xen/device_tree.h | 14 +++++
> > 3 files changed, 125 insertions(+), 0 deletions(-)
> > create mode 100644 docs/misc/arm/device-tree/booting.txt
> >
> > diff --git a/docs/misc/arm/device-tree/booting.txt
> > b/docs/misc/arm/device-tree/booting.txt
> > new file mode 100644
> > index 0000000..94cd3f1
> > --- /dev/null
> > +++ b/docs/misc/arm/device-tree/booting.txt
> > @@ -0,0 +1,25 @@
> > +Xen is passed the dom0 kernel and initrd via a reference in the /chosen
> > +node of the device tree.
> > +
> > +Each node has the form /chosen/modules/module@<N> and contains the
> > following
> > +properties:
> > +
> > +- compatible
> > +
> > + Must be:
> > +
> > + "xen,<type>", "xen,multiboot-module"
> > +
> > + where <type> must be one of:
> > +
> > + - "linux-zimage" -- the dom0 kernel
> > + - "linux-initrd" -- the dom0 ramdisk
> > +
> > +- reg
> > +
> > + Specifies the physical address of the module in RAM and the
> > + length of the module.
> > +
> > +- bootargs (optional)
> > +
> > + Command line associated with this module
> > diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> > index da0af77..4bb640e 100644
> > --- a/xen/common/device_tree.c
> > +++ b/xen/common/device_tree.c
> > @@ -270,6 +270,90 @@ static void __init process_cpu_node(const void *fdt,
> > int node,
> > cpumask_set_cpu(start, &cpu_possible_map);
> > }
> >
> > +static int __init process_chosen_modules_node(const void *fdt, int node,
> > + const char *name, int *depth,
> > + u32 address_cells, u32
> > size_cells)
> > +{
> > + const struct fdt_property *prop;
> > + const u32 *cell;
> > + int nr, nr_modules = 0;
> > + struct dt_mb_module *mod;
> > + int len;
> > +
> > + for ( *depth = 1;
> > + *depth >= 1;
> > + node = fdt_next_node(fdt, node, depth) )
> > + {
> > + name = fdt_get_name(fdt, node, NULL);
> > + if ( strncmp(name, "module@", strlen("module@")) == 0 ) {
> > +
> > + if ( fdt_node_check_compatible(fdt, node,
> > + "xen,multiboot-module" ) != 0 )
> > + early_panic("%s not a compatible module node\n", name);
> > +
> > + if ( fdt_node_check_compatible(fdt, node,
> > + "xen,linux-zimage") == 0 )
> > + nr = 1;
> > + else if ( fdt_node_check_compatible(fdt, node,
> > + "xen,linux-initrd") == 0)
> > + nr = 2;
> > + else
> > + early_panic("%s not a known xen multiboot byte\n");
> > +
> > + if ( nr > nr_modules )
> > + nr_modules = nr;
> > +
> > + mod = &early_info.modules.module[nr];
> > +
> > + prop = fdt_get_property(fdt, node, "reg", NULL);
> > + if ( !prop )
> > + early_panic("node %s missing `reg' property\n", name);
> > +
> > + cell = (const u32 *)prop->data;
> > + device_tree_get_reg(&cell, address_cells, size_cells,
> > + &mod->start, &mod->size);
> > +
> > + prop = fdt_get_property(fdt, node, "bootargs", &len);
> > + if ( prop )
> > + {
> > + if ( len > sizeof(mod->cmdline) )
> > + early_panic("module %d command line too long\n", nr);
> > +
> > + safe_strcpy(mod->cmdline, prop->data);
> > + }
> > + else
> > + mod->cmdline[0] = 0;
> > + }
> > + }
> > +
> > + for ( nr = 1 ; nr < nr_modules ; nr++ )
> > + {
> > + mod = &early_info.modules.module[nr];
> > + if ( !mod->start || !mod->size )
> > + early_panic("module %d missing / invalid\n", nr);
> > + }
> > +
> > + early_info.modules.nr_mods = nr_modules;
> > + return node;
> > +}
> > +
> > +static void __init process_chosen_node(const void *fdt, int node,
> > + const char *name,
> > + u32 address_cells, u32 size_cells)
> > +{
> > + int depth;
> > +
> > + for ( depth = 0;
> > + depth >= 0;
> > + node = fdt_next_node(fdt, node, &depth) )
> > + {
> > + name = fdt_get_name(fdt, node, NULL);
> > + if ( depth == 1 && strcmp(name, "modules") == 0 )
> > + node = process_chosen_modules_node(fdt, node, name, &depth,
> > + address_cells, size_cells);
> > + }
> > +}
> > +
> > static int __init early_scan_node(const void *fdt,
> > int node, const char *name, int depth,
> > u32 address_cells, u32 size_cells,
> > @@ -279,6 +363,8 @@ static int __init early_scan_node(const void *fdt,
> > process_memory_node(fdt, node, name, address_cells, size_cells);
> > else if ( device_tree_type_matches(fdt, node, "cpu") )
> > process_cpu_node(fdt, node, name, address_cells, size_cells);
> > + else if ( device_tree_node_matches(fdt, node, "chosen") )
> > + process_chosen_node(fdt, node, name, address_cells, size_cells);
> >
> > return 0;
> > }
>
> You have really written a lot of code here!
> I would have thought that just matching on the compatible string would
> be enough:
>
> else if ( device_tree_node_matches(fdt, node, "linux-zimage") )
> process_linuxzimage_node(fdt, node, name, address_cells, size_cells);
> else if ( device_tree_node_matches(fdt, node, "linux-initrd") )
> process_linuxinitrd_node(fdt, node, name, address_cells, size_cells);
>
> so that your process_linuxzimage_node and process_linuxinitrd_node start
> from the right node and have everything they need to parse it
Is the tree structure of Device Tree meaningless? I'd have thought that
a compatible node would only have meaning at a particular place in the
tree. Granted compatible nodes are often pretty specific and precise,
but is that inherent enough in DT that we can rely on it?
>
>
>
> > diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
> > index 4d010c0..c383677 100644
> > --- a/xen/include/xen/device_tree.h
> > +++ b/xen/include/xen/device_tree.h
> > @@ -15,6 +15,7 @@
> > #define DEVICE_TREE_MAX_DEPTH 16
> >
> > #define NR_MEM_BANKS 8
> > +#define NR_MODULES 2
> >
> > struct membank {
> > paddr_t start;
> > @@ -26,8 +27,21 @@ struct dt_mem_info {
> > struct membank bank[NR_MEM_BANKS];
> > };
> >
> > +struct dt_mb_module {
> > + paddr_t start;
> > + paddr_t size;
> > + char cmdline[1024];
> > +};
> > +
> > +struct dt_module_info {
> > + int nr_mods;
> > + /* Module 0 is Xen itself, followed by the provided modules-proper */
> > + struct dt_mb_module module[NR_MODULES + 1];
> > +};
> > +
> > struct dt_early_info {
> > struct dt_mem_info mem;
> > + struct dt_module_info modules;
> > };
> >
> > typedef int (*device_tree_node_func)(const void *fdt,
> > --
> > 1.7.9.1
> >
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